package com.java.st.lib.tools.secutiry;

import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * MD5的加密工具
 * MD5是不可逆
 * 用户的密码一般都会使用MD5进行加密
 *
 */
public class MD5Utils {
	private final static char[] hexDigits = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E',
			'F' };

	/**
	 * 2个字节的MD5加密
	 * @param input
	 * @return
	 */
	public static String md5With16(String input) {
		return code(input, 16);
	}

	/**
	 * 4个字节的Md5加密
	 * @param input
	 * @return
	 */
	public static String md5With32(String input) {
		return code(input, 32);
	}

	public static String md5With32(byte[] bytes) {
	    return code(bytes, 32);
    }

	public static String md3(String input) {
		try {
			MessageDigest md = MessageDigest.getInstance(System.getProperty("MD5.algorithm", "MD5"));
			byte[] a = md.digest(input.getBytes());
			a = md.digest(a);
			return bytesToHex(a);
		} catch (NoSuchAlgorithmException e) {
			e.printStackTrace();
		}
		return null;
	}

	private static String code(String input, int bit) {
		try {
			MessageDigest md = MessageDigest.getInstance(System.getProperty("MD5.algorithm", "MD5"));
			if (bit == 16) {
				return bytesToHex(md.digest(input.getBytes("utf-8"))).substring(8, 24);
			}
			return bytesToHex(md.digest(input.getBytes("utf-8")));
		} catch (NoSuchAlgorithmException e) {
			e.printStackTrace();
		} catch (UnsupportedEncodingException e) {
			e.printStackTrace();
		}
		return null;
	}

	private static String code(byte[] bytes, int bit) {
		if (bytes == null) {
			return null;
		}
		try {
			MessageDigest md = MessageDigest.getInstance(System.getProperty("MD5.algorithm", "MD5"));
			if (bit == 16) {
				return bytesToHex(md.digest(bytes)).substring(8, 24);
			}
			return bytesToHex(md.digest(bytes));
		} catch (NoSuchAlgorithmException e) {
			e.printStackTrace();
		}
		return null;
	}

	private static String bytesToHex(byte[] bytes) {
		StringBuffer sb = new StringBuffer();
		int t;
		for (int i = 0; i < 16; i++) {
			t = bytes[i];
			if (t < 0)
				t += 256;
			sb.append(hexDigits[(t >>> 4)]);
			sb.append(hexDigits[(t % 16)]);
		}
		return sb.toString();
	}
}
